Disabling LD2 on 10031

[Jay Beavers]

In this previous discussion on minimizing power consumption on the NRF51-Dongle, it says:

You are using evaluation kit or development kit and LEDs are connected on your board. Solution: Disconnect the LEDs or disable them in software. When using nRF51-DK or nRF51-Dongle, LEDs are not included in the current measurement.

However I don't see documentation anywhere on how to disable the 'system status' LED LD2 when it comes time to get serious about power measurement. Can you point me in the right direction?

[Hung Bui]

@Jay: How did you do power measurement ? The nRF51 was not made for doing test with power measurement because there is no separated current source between nRF51 and the Segger's chip. If you want to do power measurement, you should find a way to isolate the Segger's chip (that means also the LD2 LED).

[Jay Beavers]

Alright, here's my specific situation. I'm early into a startup and as my proof of concept I've ordered a few NRF51-Dongle boards (along with an NRF51-DK). I have my concept working now so I'm planning to deploy a few (<10) devices to customer sites for an initial pilot program.

I'm a software engineer in a startup of two people, so rather than shoot a custom board, I'm planning to use NRF51-Dongles for my pilot, alongside a 1200 mA LiPo and a step down voltage regulator. I want to minimize the power consumption overhead of the NRF51-Dongle for this pilot program so I can get a rough idea of the power lifetime of my app and also so I can maximize the battery lifetime of the pilot which will run for ~3 months.

I also have a BLE Smart Beacon kit on hand, but I prefer to stick with the Dongle boards for my pilot because it easily mounts to a 0.1" proto board so I'm not worried about my (basic) solder joints causing reliability problems over my initial pilot deployment. I like the smaller size of the Dongles vs. the DKs for pilot purposes, which I will be putting into a custom 3d printed case so as to look decent for my pilot participants.

So the heart of my question is can I through software configuration flip an NRF51-Dongle into 'production mode' that turns off excess power draw? I'd prefer to be able to flip it back into 'development mode' later as I'm not planning to implement OTA DFU for my pilot so I'll need some way to update the firmware on the pilot 'production devices'. So I'd prefer a solution that looks like a software switch rather than cutting a trace.

[Jay Beavers]

I'm planning to measure current draw by using a bench supply which shows current draw and also inserting an amp meter data logger between the bench supply and the prototype device

[Hung Bui]

I don't see any solution in this case. The Atmel chip and the nRF51 chip share the same power source, when you power the board you will power both chips. You will see about ~20uA more than what it should be. I assume this current is for the Atmel chip in sleep mode. ( Note: you should supply the current on VDD_3V3, not on VIN or VBUS, otherwise you will trigger the Atmel chip to work in USB mode and you will see the current consumption of 20mA)

If you want to use a ready made small footprint board, you can think of buying the nRF BeaconKit, then you don't have to worry about extra current. I think it would fit for your application. (You would need to use the nRF51 DK to program the kit).